The isoenzymes of glucose-6-phosphate dehydrogenase (G-6-PD) will be used as cellular markers in black females heterozygous for G-6-PD to test whether the fatty streak is the forerunner of the fibrous plaque of atherosclerosis. In addition, thrombi at various stages of organization will be studied with the same techniques to determine whether these can act as the forerunner of this fibrous plaque. BIBLIOGRAPHIC REFERENCE: Clonal characteristics of fibrous plaques and fatty streaks from human aortas. Pearson, T.A., Wang, A., Solez, K., Heptinstall, R.H., Am. J. Pathol. 81:379-387, 1975.